From pixels to druggable leads: A CADD strategy for the design and synthesis of potent DDR1 inhibitors.

BACKGROUND AND OBJECTIVE: While numerous in silico tools exist for target-based drug discovery, the inconsistent integration of in vitro data with predictive models hinders research and development productivity. This is particularly apparent during the Hit-to-Lead stage, where unreliable in-silico tools often lead to suboptimal lead selection. Herein, we address this challenge by presenting a CADD-guided pipeline that successfully integrates rational drug design with in-silico hits to identify a promising DDR1 lead. METHODS: 2 × 1000 ns MD simulations along with their respective FEL and MMPBSA analyses were employed to guide the rational design and synthesis of 12 novel compounds which were evaluated for their DDR inhibition. RESULTS: The molecular dynamics investigation of the initial hit led to the identification of key structural features within the DDR1 binding pocket. The identified key features were used to guide the rational design and synthesis of twelve novel derivatives. SAR analysis, biological evaluation, molecular dynamics, and free energy calculations were carried out for the synthesized derivatives to understand their mechanism of action. Compound 4c exhibited the strongest inhibition and selectivity for DDR1, with an IC50 of 0.11 µM. CONCLUSIONS: The MD simulations led to the identification of a key hydrophobic groove in the DDR1 binding pocket. The integrated approach of SAR analysis with molecular dynamics led to the identification of compound 4c as a promising lead for further development of potent and selective DDR1 inhibitors. Moreover, this work establishes a protocol for translating in silico hits to real world bioactive druggable leads.

A novel indole derivative, 2-{3-[1-(benzylsulfonyl)piperidin-4-yl]-2-methyl-1H-indol-1-yl}-1-(pyrrolidin-1-yl)ethenone, suppresses hedgehog signaling and drug-resistant tumor growth.

The Hedgehog (Hh) signaling pathway plays important roles in various physiological functions. Several malignancies, such as basal cell carcinoma (BCC) and medulloblastoma (MB), have been linked to the aberrant activation of Hh signaling. Although therapeutic drugs have been developed to inhibit Hh pathway-dependent cancer growth, drug resistance remains a major obstacle in cancer treatment. Here, we show that the newly identified, 2-{3-[1-(benzylsulfonyl)-1,2,3,6-tetrahydropyridin-4-yl]-2-methyl-1H-indol-1-yl}-1-(pyrrolidin-1-yl)ethenone analog (LKD1214) exhibits comparable potency to vismodegib in suppressing the Hh pathway activation. LKD1214 represses Smoothened (SMO) activity by blocking its ciliary translocation. Interestingly, we also identified that it has a distinctive binding interface with SMO compared with other SMO-regulating chemicals. Notably, it maintains an inhibitory activity against the SmoD477H mutant, as observed in a patient with vismodegib-resistant BCC. Furthermore, LKD1214 inhibits tumor growth in the mouse model of MB. Collectively, these findings suggest that LKD1214 has the therapeutic potential to overcome drug-resistance in Hh-dependent cancers.

PT-Finder: A multi-modal neural network approach to target identification.

Efficient target identification for bioactive compounds, including novel synthetic analogs, is crucial for accelerating the drug discovery pipeline. However, the process of target identification presents significant challenges and is often expensive, which in turn can hinder the drug discovery efforts. To address these challenges machine learning applications have arisen as a promising approach for predicting the targets for novel chemical compounds. These methods allow the exploration of ligand-target interactions, uncovering of biochemical mechanisms, and the investigation of drug repurposing. Typically, the current target identification tools rely on assessing ligand structural similarities. Herein, a multi-modal neural network model was built using a library of proteins, their respective sequences, and active inhibitors. Subsequent validations showed the model to possess accuracy of 82 % and MPRAUC of 0.80. Leveraging the trained model, we developed PT-Finder (Protein Target Finder), a user-friendly offline application that is capable of predicting the target proteins for hundreds of compounds within a few seconds. This combination of offline operation, speed, and accuracy positions PT-Finder as a powerful tool to accelerate drug discovery workflows. PT-Finder and its source codes have been made freely accessible for download at https://github.com/PT-Finder/PT-Finder.

Natural products as IL-6 inhibitors for inflammatory diseases: Synthetic and SAR perspective.

Interleukin-6 (IL-6), a pleiotropic cytokine, plays a pivotal role in the pathophysiology of various diseases including diabetes, atherosclerosis, Alzheimer's disease, multiple myeloma, rheumatoid arthritis, and prostate cancer. The signaling pathways associated with IL-6 offer promising targets for therapeutic interventions in inflammatory diseases and IL-6-dependent tumors. Although certain anti-IL-6 monoclonal antibodies are currently employed clinically, their usage is hampered by drawbacks such as high cost and potential immunogenicity, limiting their application. Thus, the imperative arises to develop novel small non-peptide molecules acting as IL-6 inhibitors. Various natural products derived from diverse sources have been investigated for their potential to inhibit IL-6 activity. Nevertheless, these natural products remain inadequately explored in terms of their structure-activity relationships. In response, our review aims to provide syntheses and structure activity perspective of natural IL-6 inhibitors. The comprehensive amalgamation of information presented in this review holds the potential to serve as a foundation for forthcoming research endeavors by medicinal chemists, facilitating the design of innovative IL-6 inhibitors to address the complexities of inflammatory diseases.

Machine Learning-Based Approach to Developing Potent EGFR Inhibitors for Breast Cancer-Design, Synthesis, and In Vitro Evaluation.

The epidermal growth factor receptor (EGFR) is vital for regulating cellular functions, including cell division, migration, survival, apoptosis, angiogenesis, and cancer. EGFR overexpression is an ideal target for anticancer drug development as it is absent from normal tissues, marking it as tumor-specific. Unfortunately, the development of medication resistance limits the therapeutic efficacy of the currently approved EGFR inhibitors, indicating the need for further development. Herein, a machine learning-based application that predicts the bioactivity of novel EGFR inhibitors is presented. Clustering of the EGFR small-molecule inhibitor (∼9000 compounds) library showed that N-substituted quinazolin-4-amine-based compounds made up the largest cluster of EGFR inhibitors (∼2500 compounds). Taking advantage of this finding, rational drug design was used to design a novel series of 4-anilinoquinazoline-based EGFR inhibitors, which were first tested by the developed artificial intelligence application, and only the compounds which were predicted to be active were then chosen to be synthesized. This led to the synthesis of 18 novel compounds, which were subsequently evaluated for cytotoxicity and EGFR inhibitory activity. Among the tested compounds, compound 9 demonstrated the most potent antiproliferative activity, with 2.50 and 1.96 µM activity over MCF-7 and MDA-MB-231 cancer cell lines, respectively. Moreover, compound 9 displayed an EGFR inhibitory activity of 2.53 nM and promising apoptotic results, marking it a potential candidate for breast cancer therapy.

Cantharidin-Based Verbenone Derivatives as a Novel Insecticide against Plutella xylostella: Design, Synthesis, Insecticidal Activity Evaluation, and 3D QSAR Study.

The diamondback moth is a detrimental insect pest of brassicaceous crops which was among the first crop insects to be reported as DDT resistant. It has since proven to be significantly resistant to nearly every synthetic insecticide used in the field in many crucifer-producing regions. Due to insecticide control failures in some parts of the world, economically viable crucifer production is now all but impossible. As a result, there has been an increasing effort to identify new compounds with strong pesticidal activity. Cantharidin is one such compound that has been shown to be highly effective against a variety of insect pests. However, its chemical synthesis and potential toxicity to non-target organisms have been a major source of concern. Herein, using rational design approaches, a new series of cantharidin-based verbenone derivatives were synthesized and evaluated for their insecticidal activities against the diamondback moth. Among different compounds screened, compounds 6a, 6h, 6i, and 6q emerged as the most potent compounds exhibiting 100% mortality at a concentration of 100 mg/L after four days. These compounds demonstrated a good anti-feeding effect against the diamondback moth on cabbage leaves. Subsequently, a 3D QSAR study was carried out to identify the key structural features of the synthesized compounds and their correlation with insecticidal activity.

Integration of Hybridization Strategies in Pyridine-Urea Scaffolds for Novel Anticancer Agents: Design, Synthesis, and Mechanistic Insights.

Annually, millions of new cancer cases are reported, leading to millions of deaths worldwide. Among the newly reported cases, breast and colon cancers prevail as the most frequently detected variations. To effectively counteract this rapid increase, the development of innovative therapies is crucial. Small molecules possessing pyridine and urea moieties have been reported in many of the currently available anticancer agents, especially VEGFR2 inhibitors. With this in mind, a rational design approach was employed to create hybrid small molecules combining urea and pyridine. These synthesized compounds underwent in vitro testing against breast and colon cancer cell lines, revealing potent submicromolar anticancer activity. Compound 8a, specifically, exhibited an impressive GI50 value of 0.06 µM against the MCF7 cancer cell line, while compound 8h displayed the highest cytotoxic activity against the HCT116 cell line, with a GI50 of 0.33 ± 0.042 µM. Notably, compounds 8a, 8h, and 8i demonstrated excellent safety profiles when tested on normal cells. Molecular docking, dynamic studies, and free energy calculations were employed to validate the affinity of these compounds as VEGFR2 inhibitors.

Small Molecule c-KIT Inhibitors for the Treatment of Gastrointestinal Stromal Tumors: A Review on Synthesis, Design Strategies, and Structure-Activity Relationship (SAR).

The proto-oncogenic protein, c-KIT, plays a crucial role in regulating cellular transformation and differentiation processes, such as proliferation, survival, adhesion, and chemotaxis. The overexpression of, and mutations, in c-KIT can lead to its dysregulation and promote various human cancers, particularly gastrointestinal stromal tumors (GISTs); approximately 80-85% of cases are associated with oncogenic mutations in the KIT gene. Inhibition of c-KIT has emerged as a promising therapeutic target for GISTs. However, the currently approved drugs are associated with resistance and significant side effects, highlighting the urgent need to develop highly selective c-KIT inhibitors that are not affected by these mutations for GISTs. Herein, the recent research efforts in medicinal chemistry aimed at developing potent small-molecule c-KIT inhibitors with high kinase selectivity for GISTs are discussed from a structure-activity relationship perspective. Moreover, the synthetic pathways, pharmacokinetic properties, and binding patterns of the inhibitors are also discussed to facilitate future development of more potent and pharmacokinetically stable small-molecule c-KIT inhibitors.

Identification of Potent hDHODH Inhibitors for Lung Cancer via Virtual Screening of a Rationally Designed Small Combinatorial Library.

Cancer is characterized by altered cellular metabolism, and metabolic enzymes are considered as a promising target for anticancer therapy. Pyrimidine metabolism dysregulation is associated with various types of cancer, particularly lung cancer, which is one of the leading causes of cancer-related mortality worldwide. Recent studies have shown that small-cell lung cancer cells are particularly reliant on the pyrimidine biosynthesis pathway and are sensitive to its disruption. DHODH, the rate-limiting enzyme of the de novo pyrimidine production pathway, is essential in the production of RNA and DNA and is overexpressed in malignancies such as AML, skin cancer, breast cancer, and lung cancer, thereby highlighting DHODH as a viable target for developing drugs to combat lung cancer. Herein, rational drug design and computational techniques were used to discover novel DHODH inhibitors. A small combinatorial library was generated, and the top hits were synthesized and tested for anticancer activity against three lung cancer cell lines. Among the tested compounds, compound 5c possessed a stronger cytotoxicity (TC50 of 11 µM) compared to the standard FDA-approved drug (Regorafenib, TC50 of 13 µM) on the A549 cell line. Furthermore, compound 5c demonstrated potent inhibitory activity against hDHODH at a nanomolar level of 421 nM. DFT, molecular docking, molecular dynamic simulations, and free energy calculations were also carried out to understand the inhibitory mechanisms of the synthesized scaffolds. These in silico studies identified key mechanisms and structural features that will be crucial for future studies.

Design, Synthesis and Biological Evaluation of Novel MDH Inhibitors Targeting Tumor Microenvironment.

MDH1 and MDH2 enzymes play an important role in the survival of lung cancer. In this study, a novel series of dual MDH1/2 inhibitors for lung cancer was rationally designed and synthesized, and their SAR was carefully investigated. Among the tested compounds, compound 50 containing a piperidine ring displayed an improved growth inhibition of A549 and H460 lung cancer cell lines compared with LW1497. Compound 50 reduced the total ATP content in A549 cells in a dose-dependent manner; it also significantly suppressed the accumulation of hypoxia-inducible factor 1-alpha (HIF-1α) and the expression of HIF-1α target genes such as GLUT1 and pyruvate dehydrogenase kinase 1 (PDK1) in a dose-dependent manner. Furthermore, compound 50 inhibited HIF-1α-regulated CD73 expression under hypoxia in A549 lung cancer cells. Collectively, these results indicate that compound 50 may pave the way for the development of next-generation dual MDH1/2 inhibitors to target lung cancer.

Perspective for Discovery of Small Molecule IL-6 Inhibitors through Study of Structure-Activity Relationships and Molecular Docking.

Interleukin-6 (IL-6) is a proinflammatory cytokine that plays a key role in the pathogenesis and physiology of inflammatory and autoimmune diseases, such as coronary heart disease, cancer, Alzheimer's disease, asthma, rheumatoid arthritis, and most recently COVID-19. IL-6 and its signaling pathway are promising targets in the treatment of inflammatory and autoimmune diseases. Although, anti-IL-6 monoclonal antibodies are currently being used in clinics, huge unmet medical needs remain because of the high cost, administration-related toxicity, lack of opportunity for oral dosing, and potential immunogenicity of monoclonal antibody therapy. Furthermore, nonresponse or loss of response to monoclonal antibody therapy has been reported, which increases the importance of optimizing drug therapy with small molecule drugs. This work aims to provide a perspective for the discovery of novel small molecule IL-6 inhibitors by the analysis of the structure-activity relationships and computational studies for protein-protein inhibitors targeting the IL-6/IL-6 receptor/gp130 complex.

Discovery and optimization of natural-based nanomolar c-Kit inhibitors via in silico and in vitro studies.

c-Kit is a receptor tyrosine kinase which is involved in intracellular signaling and mutations of c-Kit have been associated with various types of cancers. Investigations have shown that inhibition of c-Kit, using tyrosine kinase inhibitors, yielded promising results in cancer treatment marking it as a promising target for cancer therapy. However, the emerging resistance for the current therapy necessitates the development of more potent inhibitors which are not affected by these mutations. Herein, virtual screening of a library of natural-based compounds yielded three hits (2, 5 and 6) which possessed nanomolar inhibitory (2.02, 4.33 and 2.80 nM, respectively) activity when tested in vitro against c-Kit. Single point mutation docking studies showed the hits to be unaffected by the most common resistance mutation in imatinib-resistant cells, mutation of Val654. Although, the top hits exhibited around 3000 higher inhibitory potency toward c-Kit when compared to imatinib (5.4 µM), previous studies have shown that they are metabolically unstable. Fragment-based drug design approaches were then employed to enhance binding affinity of the top hit and make it more metabolically stable. Screening of the generated fragments yielded a new derivative, F1, which demonstrated stronger binding affinity, stability and binding free energy when compared to the hit compound 2.Communicated by Ramaswamy H. Sarma.

Identification of 1H-purine-2,6-dione derivative as a potential SARS-CoV-2 main protease inhibitor: molecular docking, dynamic simulations, and energy calculations.

The rapid spread of the coronavirus since its first appearance in 2019 has taken the world by surprise, challenging the global economy, and putting pressure on healthcare systems across the world. The introduction of preventive vaccines only managed to slow the rising death rates worldwide, illuminating the pressing need for developing effective antiviral therapeutics. The traditional route of drug discovery has been known to require years which the world does not currently have. In silico approaches in drug design have shown promising results over the last decade, helping to decrease the required time for drug development. One of the vital non-structural proteins that are essential to viral replication and transcription is the SARS-CoV-2 main protease (Mpro). Herein, using a test set of recently identified COVID-19 inhibitors, a pharmacophore was developed to screen 20 million drug-like compounds obtained from a freely accessible Zinc database. The generated hits were ranked using a structure based virtual screening technique (SBVS), and the top hits were subjected to in-depth molecular docking studies and MM-GBSA calculations over SARS-COV-2 Mpro. Finally, the most promising hit, compound (1), and the potent standard (III) were subjected to 100 ns molecular dynamics (MD) simulations and in silico ADME study. The result of the MD analysis as well as the in silico pharmacokinetic study reveal compound 1 to be a promising SARS-Cov-2 MPro inhibitor suitable for further development.

Novel cudraisoflavone J derivatives as potent neuroprotective agents for the treatment of Parkinson's disease via the activation of Nrf2/HO-1 signaling.

Parkinson's disease (PD) is a neurodegenerative disorder that causes uncontrollable movements. Although many breakthroughs in PD therapy have been accomplished, there is currently no cure for PD, and only trials to relieve symptoms have been evaluated. Recently, we reported the total synthesis of cudraisoflavone J and its chiral isomers [Lu et al., J. Nat. Prod. 2021, 84, 1359]. In this study, we designed and synthesized a series of novel cudraisoflavone J derivatives and evaluated their neuroprotective activities in neurotoxin-treated PC12 cells. Among these compounds, difluoro-substituted derivative (13m) and prenylated derivative (24) provided significant protection to PC12 cells against toxicity induced by 6-hydroxydopamine (6-OHDA) or rotenone. Both derivatives inhibited 6-OHDA- or rotenone-induced production of reactive oxygen species and partially attenuated lipid peroxidation in rat brain homogenates, indicating their antioxidant properties. They also increased the expression of the antioxidant enzyme, heme oxygenase (HO)-1, and enhanced the nuclear translocation of Nrf2, the transcription factor that regulates the expression of antioxidant proteins. The neuroprotective effects of 13m and 24 were eliminated by Zn(II)-protoporphyrin IX, an HO-1 inhibitor, demonstrating the critical role of HO-1 in their actions. Moreover, upregulation of HO-1 was abolished by nuclear factor erythroid 2-related factor (Nrf2) knockdown, verifying that Nrf2 is an upstream regulator of HO-1. Compounds 13m and 24 triggered phosphorylation of ERK1/2, JNK, and Akt. Most importantly, 13m- and 24-induced enhancement of Nrf2 translocation and HO-1 expression was reversed by U0126 (an ERK inhibitor), SP600125 (a JNK inhibitor), and LY294002 (an Akt inhibitor). Collectively, our results show that compounds 13m and 24 exert neuroprotective and antioxidant effects through the Nrf2/HO-1 pathway mediated by phosphorylation of ERK1/2, JNK, or Akt in PC12 cells. Based on our findings, both derivatives could serve as potential therapeutic candidates for the neuroprotective treatment of PD.

4-Anilinoquinazoline-based benzenesulfonamides as nanomolar inhibitors of carbonic anhydrase isoforms I, II, IX, and XII: design, synthesis, in-vitro, and in-silico biological studies.

Human carbonic anhydrase inhibitors (hCAIs) are a key therapeutic class with a multitude of novel applications such as anticonvulsants, topically acting antiglaucoma, and anticancer drugs. Herein, a new series of 4-anilinoquinazoline-based benzenesulfonamides were designed, synthesised, and biologically assessed as potential hCAIs. The target compounds are based on the well-tolerated kinase scaffold (4-anilinoquinazoline). Compounds 3a (89.4 nM), 4e (91.2 nM), and 4f (60.9 nM) exhibited 2.8, 2.7, and 4 folds higher potency against hCA I when compared to the standard (AAZ, V), respectively. A single digit nanomolar activity was elicited by compounds 3a (8.7 nM), 4a (2.4 nM), and 4e (4.6 nM) with 1.4, 5, and 2.6 folds of potency compared to AAZ (12.1 nM) against isoform hCA II, respectively. Structure-activity relationship (SAR) and molecular docking studies validated our design approach that revealed highly potent hCAIs.

Identification of Novel and Potent Indole-Based Benzenesulfonamides as Selective Human Carbonic Anhydrase II Inhibitors: Design, Synthesis, In Vitro, and In Silico Studies.

In recent decades, human carbonic anhydrase inhibitors (hCAIs) have emerged as an important therapeutic class with various applications including antiglaucoma, anticonvulsants, and anticancer agents. Herein, a novel series of indole-based benzenesulfonamides were designed, synthesized, and biologically evaluated as potential hCAIs. A regioisomerism of the sulfonamide moiety was carried out to afford a total of fifteen indole-based benzenesulfonamides possessing different amide linkers that enable the ligands to be flexible and develop potential H-bond interaction(s) with the target protein. The activity of the synthesized compounds was evaluated against four hCA isoforms (I, II, IX and, XII). Compounds 2b, 2c, 2d, 2f, 2h and 2o exhibited potent and selective profiles over the hCA II isoform with Ki values of 7.3, 9.0, 7.1, 16.0, 8.6 and 7.5 nM, respectively. Among all, compound 2a demonstrated the most potent inhibition against the hCA II isoform with an inhibitory constant (Ki) of 5.9 nM, with 13-, 34-, and 9-fold selectivity for hCA II over I, IX and XII isoforms, respectively. Structure-activity relationship data attained for various substitutions were rationalized. Furthermore, a molecular docking study gave insights into both inhibitory activity and selectivity of the target compounds. Accordingly, this report presents a successful scaffold hoping approach that reveals compound 2a as a highly potent and selective indole-based hCA II inhibitor worthy of further investigation.

Identification of novel discoidin domain receptor 1 (DDR1) inhibitors using E-pharmacophore modeling, structure-based virtual screening, molecular dynamics simulation and MM-GBSA approaches.

Dysregulation of the discoidin domain receptor (DDR1), a collagen-activated receptor tyrosine kinase, has been linked to several human cancer diseases including non-small cell lung carcinoma (NSCLC), ovarian cancer, glioblastoma, and breast cancer, in addition to several inflammatory and neurological conditions. Although there are some selective DDR1 inhibitors that have been discovered during the last two decades, a combination of elevated cytotoxicity, kinome selectivity and/or poor DMPK profile has prevented more in-depth studies from being performed. As such, no DDR1 inhibitor has reached clinical investigation to date, forming an urgent need to develop specific DDR1 inhibitor(s) using various drug discovery means. However, the recent discovery of VU6015929, a potent and selective DDR1 kinase inhibitor, with enhanced physiochemical and DMPK properties in addition to its clean kinome profile marked a milestone in the development of DDR1 inhibitors. Herein, VU6015929 was used to construct a 3D e-pharmacophore model which was validated via calculating the difference of score between the active compounds and decoys. The validated e-pharmacophore model was then utilized to screen 20 million drug-like compounds obtained from the freely accessible Zinc database. The generated hits were ranked using high throughput virtual screening technique (HTVS), and the top 8 small molecules were subjected to a molecular docking study and MM-GBSA calculations. Protein-ligand complexes of compounds 1, 2, 3 and the standard compound (VU6015929) were performed for 100 ns and compared with the DDR1 unbound protein state and the DDR1 bound to a co-crystallized ligand. The molecular docking, MD and MM-GBSA outputs revealed compounds 1-3 as potential DDR1 inhibitors, with compound 2 displaying superior binding affinity, comparable binding stability and average binding free energy for the ligand-enzyme complex compared to VU6015929.

Hit Identification of a Novel Quinazoline Sulfonamide as a Promising EphB3 Inhibitor: Design, Virtual Combinatorial Library, Synthesis, Biological Evaluation, and Docking Simulation Studies.

EphB3 is a major key player in a variety of cellular activities, including cell migration, proliferation, and apoptosis. However, the exact role of EphB3 in cancer remains ambiguous. Accordingly, new EphB3 inhibitors can increase the understanding of the exact roles of the receptor and may act as promising therapeutic candidates. Herein, a hybrid approach of structure-based design and virtual combinatorial library generated 34 quinazoline sulfonamides as potential selective EphB3 inhibitors. A molecular docking study over EphB3 predicted the binding affinities of the generated library, and the top seven hit compounds (3a and 4a-f), with GlideScore ≥ -6.20 Kcal/mol, were chosen for further MM-GBSA calculations. Out of the seven top hits, compound 4c showed the highest MM-GBSA binding free energy (-74.13 Kcal/mol). To validate these predicted results, compounds 3a and 4a-f were synthesized and characterized using NMR, HRMS, and HPLC. The biological evaluation revealed compound 4c as a potent EphB3 inhibitory lead (IC50 = 1.04 µM). The screening of 4c over a mini-panel of kinases consisting of EGFR, Aurora A, Aurora B, CDK2/cyclin A, EphB1, EphB2, EphB4, ERBB2/HER2, and KDR/VEGFR2, showed a promising selective profile against EphB3 isoform. A dose-dependent assay of compound 4c and a molecular docking study over the different forms of EphB provided insights into the elicited biological activities and highlighted reasonable explanations of the selectivity.

Melatonin Analogues Potently Inhibit MAO-B and Protect PC12 Cells against Oxidative Stress.

Monoamine oxidase B (MAO-B) metabolizes dopamine and plays an important role in oxidative stress by altering the redox state of neuronal and glial cells. MAO-B inhibitors are a promising therapeutical approach for Parkinson's disease (PD). Herein, 24 melatonin analogues (3a-x) were synthesized as novel MAO-B inhibitors with the potential to counteract oxidative stress in neuronal PC12 cells. Structure elucidation, characterization, and purity of the synthesized compounds were performed using 1H-NMR, 13C-NMR, HRMS, and HPLC. At 10 µM, 12 compounds showed >50% MAO-B inhibition. Among them, compounds 3n, 3r, and 3u-w showed >70% inhibition of MAO-B and IC50 values of 1.41, 0.91, 1.20, 0.66, and 2.41 µM, respectively. When compared with the modest selectivity index of rasagiline (II, a well-known MAO-B inhibitor, SI > 50), compounds 3n, 3r, 3u, and 3v demonstrated better selectivity indices (SI > 71, 109, 83, and 151, respectively). Furthermore, compounds 3n and 3r exhibited safe neurotoxicity profiles in PC12 cells and reversed 6-OHDA- and rotenone-induced neuronal oxidative stress. Both compounds significantly up-regulated the expression of the anti-oxidant enzyme, heme oxygenase (HO)-1. Treatment with Zn(II)-protoporphyrin IX (ZnPP), a selective HO-1 inhibitor, abolished the neuroprotective effects of the tested compounds, suggesting a critical role of HO-1 up-regulation. Both compounds increased the nuclear translocation of Nrf2, which is a key regulator of the antioxidative response. Taken together, these data show that compounds 3n and 3r could be further exploited for their multi-targeted role in oxidative stress-related PD therapy.

Development of New Meridianin/Leucettine-Derived Hybrid Small Molecules as Nanomolar Multi-Kinase Inhibitors with Antitumor Activity.

Although the sea ecosystem offers a broad range of bioactivities including anticancer, none of the FDA-approved antiproliferative protein kinase inhibitors are derived from a marine source. In a step to develop new marine-inspired potent kinase inhibitors with antiproliferative activities, a new series of hybrid small molecules (5a-5g) was designed and synthesized based on chemical moieties derived from two marine natural products (Meridianin E and Leucettamine B). Over a panel of 14 cancer-related kinases, a single dose of 10 µM of the parent hybrid 5a possessing the benzo[d][1,3]dioxole moiety of Leucettamine B was able to inhibit the activity of FMS, LCK, LYN, and DAPK1 kinases with 82.5 ± 0.6, 81.4 ± 0.6, 75.2 ± 0.0, and 55 ± 1.1%, respectively. Further optimization revealed the most potent multiple kinase inhibitor of this new series (5g) with IC50 values of 110, 87.7, and 169 nM against FMS, LCK, and LYN kinases, respectively. Compared to imatinib (FDA-approved multiple kinase inhibitor), compound 5g was found to be ~ 9- and 2-fold more potent than imatinib over both FMS and LCK kinases, respectively. In silico docking simulation models of the synthesized compounds within the active site of FMS, LCK, LYN, and DAPK1 kinases offered reasonable explanations of the elicited biological activities. In an in vitro anticancer assay using a library of 60 cancer cell lines that include blood, lung, colon, CNS, skin, ovarian, renal, prostate, and breast cancers, it was found that compound 5g was able to suppress 60 and 70% of tumor growth in leukemia SR and renal RXF 393 cell lines, respectively. Moreover, an ADME study indicated a suitable profile of compound 5g concerning cell permeability and blood-brain barrier (BBB) impermeability, avoiding possible CNS side effects. Accordingly, compound 5g is reported as a potential lead towards novel antiproliferative marine-derived kinase modulators.